JPH0337844B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial application field) Improvement of electrical and magnetic properties of unidirectional silicon steel sheets,
In particular, the remarkable development efforts made in recent years to meet the extreme requirements of reducing iron loss are gradually bearing fruit, but one serious problem associated with their implementation is the use of grain-oriented silicon steel sheets. It has been pointed out that when a so-called strain relief annealing is applied after the initial processing and assembly, the deterioration of characteristics inevitably occurs, resulting in restrictions on usage. In this specification, the following is related to the results of research and development to open up a new method that can advantageously meet the above requirements, regardless of whether or not it undergoes a high-temperature thermal history such as strain relief annealing. state As is well known, unidirectional silicon steel sheets are products in which secondary recrystallized grains are highly concentrated in the (110) [001], or Goss, orientation, and are mainly used in transformers and other electrical equipment. Used as an iron core, the product is required to have high electrical and magnetic characteristics such as high magnetic flux density (represented by the B ₁₀ value) and low iron loss (represented by the W _17/50 value). This unidirectional silicon steel plate is manufactured through a wide variety of complicated processes, but numerous inventions and improvements have been made so far, and today products with a thickness of 0.30mm have magnetic properties of B ₁₀ 1.90T or more, W _{17/ 50} 1.50W/Kg or less, and the magnetic properties of products with a plate thickness of 0.23mm are B ₁₀ 1.89T
As described above, ultra-low core loss unidirectional silicon steel sheets with a W _17/50 of 0.90 W/Kg or less are being manufactured. In particular, recently there has been a marked increase in the demand for reducing power loss as a top priority from the standpoint of energy conservation.・The "Evaluation" (iron loss evaluation) system is becoming widespread. (Prior art) Under these circumstances, recently, a method has been developed in which micro-strain is introduced into the surface of a unidirectional silicon steel plate after final annealing by laser irradiation in a direction approximately perpendicular to the rolling direction to subdivide the magnetic domains. It was proposed to reduce iron loss by
−53419, Special Publication No. 58-26405 and Special Publication No. 58-
(Refer to each publication No. 26406). This magnetic domain refining technology is effective for transformer materials for laminated cores that are not subjected to strain relief annealing, but it is difficult to introduce by laser irradiation for transformer materials for rolled cores that are subjected to strain relief annealing. There is a drawback that the laser irradiation effect is lost because the localized minute strain is released by the annealing treatment and the magnetic domain width becomes wider. On the other hand, earlier in Japanese Patent Publication No. 52-24499, the surface of a unidirectional silicon steel plate after finish annealing was mirror-finished, or the mirror-finished surface was coated with metal thinning or an insulating coating was applied thereon. A method of manufacturing an ultra-low core loss unidirectional silicon steel sheet by coating and baking has been proposed. However, this method of improving iron loss through mirror finishing cannot be adopted from a process perspective, as it does not contribute enough to reducing iron loss at the cost of a significant increase in costs. Due to problems with adhesion, it has not been adopted in current manufacturing processes. Japanese Patent Publication No. 56-4150 also proposes a method in which a thin film of oxide ceramics is deposited after mirror-finishing the surface of a steel plate. However, this method cannot be used in actual manufacturing processes because the steel sheet and the ceramic layer will separate when subjected to high-temperature annealing at 600° C. or higher. (Problems to be Solved by the Invention) The inventors have attempted to overcome the disadvantage of increased costs, especially from the perspective of today's development of energy-saving materials, by taking advantage of the effect of improving iron loss due to the mirror finish described above. properties, especially the adhesion of the insulating layer without deterioration even during high-temperature treatment.
We believe that overcoming the problem of durability is essential, and based on this basic understanding, we fundamentally reexamined the method of processing steel sheets after mirror finishing and arrived at this invention. (Means for solving the problem) Here, a unidirectional silicon steel plate finished in a mirror-like state with a center line average roughness of 0.4 μm or less is heated at 600 to 1000°C and treated with a compound containing Ti (for example, TiCl ₂ , _{TiN , _ _ _}
After forming an ultra-thin tension coating of TiC or Ti(CN), annealing is performed in an _H2 atmosphere at a temperature range of 600 to 1000℃, or after that, phosphate and colloidal silica, which are the main components, are added to the tension coating. This is a method of manufacturing an ultra-low iron loss unidirectional silicon steel sheet, which comprises forming an insulating coating. An experimental example that led to the success of this invention will be described. C: 0.045% by weight (hereinafter simply expressed as %), Si:
3.38%, Mn: 0.063%, Se: 0.021%, Sb: 0.025
%, Mo: Continuously cast silicon steel slab containing 0.025%
After heating at 1340°C for 4 hours, it was hot rolled to obtain a 2.0 mm thick hot rolled sheet. Thereafter, after uniform annealing at 900°C for 3 minutes, cold rolling was performed twice with intermediate annealing at 950°C for 3 minutes to obtain a final cold-rolled plate with a thickness of 0.23 mm. After decarburization and primary recrystallization annealing in wet hydrogen at 820℃, Al ₂ O ₃ (70%) and MgO are added to the surface of the steel sheet.
(30%) was applied as a main component, and then secondary recrystallization annealing was performed at 850°C for 50 hours and blunting annealing at 1200°C in dry hydrogen for 5 hours. After that, the steel plate surface was first pickled in 50°C HCl solution to remove oxides on the steel plate surface, and then chemically polished in a solution of 3% HF and H ₂ O ₂ to give the steel plate surface a center line average roughness of 0.05μ.
The following treatments were applied to two types of samples finished in a mirror-like state. (1) A CVD reaction was carried out on the steel plate surface for 20 hours at 750°C in a mixed gas atmosphere of TiCl ₄ , H ₂ and N ₂ using a CVD equipment, and TiN was deposited on the steel plate surface.
(0.6 μm thick) was formed (a). After this CVD treatment, one part of the sample was further annealed at 750° C. for 10 hours in an H ₂ gas atmosphere (b). (2) Similarly, CVD was performed on the steel plate surface at 850℃ for 5 hours in a mixed gas atmosphere of TiCl ₄ , H ₂ and CH ₄ .
React to form TiC (0.5μm thick) on the steel plate surface
(c) caused. After this CVD treatment, one part of the sample was further annealed (d) at 700° C. for 15 hours in an H ₂ gas atmosphere. The magnetic properties of the product obtained in this way are
Table 1 shows the surface condition and the analysis values of C and N in the steel in comparison with a unidirectional silicon steel plate (e) made using a normal procedure.

[Table] * ○ Good △ Bad As is clear from Table 1, an ultra-thin tension film of TiN or TiC was formed on the surface of the unidirectional silicon steel plate by CVD treatment after mirror polishing (a) to (d) Under the conditions, the iron loss is 0.64 to 0.70 W/Kg, which is extremely extreme compared to the iron loss of 0.88 W/Kg under the condition (e) where the mirror finish and ultra-thin tension coating are not formed (comparison material processed in the normal process). It is noteworthy that it shows good iron loss. However, under the treatment conditions (a) to (d), the steel plate surface condition of products (a) and (c) was found to be sticky, which appears to be due to some residual TiCl ₄ , and there is no adverse effect on the steel plate such as surface oxidation. There is no cause for concern. On the other hand, (b) and
Under the treatment conditions (d), the surface condition of the steel plate is good due to the addition of _H2 atmosphere annealing, and the iron loss is 0.64~
It is noteworthy that it exhibits an ultra-low iron loss of 0.65W/Kg. (Operation) The reason why the above-mentioned ultra-low iron loss is achieved according to this invention has not been completely elucidated, but
_H2 atmosphere annealing after forming an ultra-thin tension film of TiN, TiC or Ti(CN) on the surface of the steel sheet further promotes purification as is clear from the analytical values of C and N in the steel shown in Table 1. This is thought to be because the H ₂ annealing resulted in a more complete coating of TiN and TiC, which enabled more elastic tension to be applied to the steel sheet. In this way, CVD treatment creates TiN on the surface of the steel plate.
After forming an ultra-thin tension film of TiC and Ti(CN),
Furthermore, by performing annealing in an H ₂ atmosphere, it is possible to further improve iron loss and improve the surface condition of the steel sheet. The improvement in properties achieved by this invention is similar to that of mirror-finished steel sheets.
TiN, TiC, Ti(C,
A strong tension is applied to the surface of the silicon steel sheet while maintaining strong adhesion with the ultra-thin film of N), achieving ultra _- low iron loss unparalleled in the past. As a result, further purification of the steel plate is achieved. Since the function of plastic microstrain is not used here, there is no problem with thermal stability, and the electrical and magnetic properties are not affected by high-temperature thermal history such as strain relief annealing. Here, the center average roughness of the finished surface is Ra≦0.4μ
It is necessary to have a mirror surface state of Ra>0.4μm.
In this case, sufficient iron loss reduction cannot be expected because the surface is rough. Next, the thickness of the tension insulating film is suitable within the range of 0.05 to 1 μm; if it is less than 0.05 μm, it will not be able to contribute to providing the necessary tension, while if it exceeds 1 μm,
This results in disadvantages in space factor and adhesion. Next, the manufacturing process of a unidirectional silicon steel plate according to the present invention will be explained. The starting material has conventionally known unidirectional silicon steel plate material components, such as C: 0.03-0.05%, Si: 2.50-4.5%, Mn:
0.01~0.2%, Mo: 0.003~0.1%, Sb: 0.005~
0.2%, total of one or two types of S or Se,
Composition containing 0.005-0.05% C: 0.03-0.08%, Si: 2.0-4.0%, S:
0.005~0.05%, N: 0.001~0.01%, Al: 0.01~
0.06%, Sn: 0.01~0.5%, Cu: 0.01~0.3%,
Composition containing Mn: 0.01-0.2% C: 0.03-0.06%, Si: 2.0-4.0%, S:
0.005~0.05%, B: 0.0003~0.0040%, N:
It is applicable to compositions containing 0.001 to 0.01% and Mn: 0.01 to 0.2%. Next, the hot-rolled sheet is subjected to uniform annealing at 800 to 1100℃ as necessary, and then cold-rolled once to achieve the final thickness1.
Double cold rolling method or double cold rolling method, which usually involves intermediate annealing at 850℃ to 1050℃ and then further cold rolling.In the latter case, the initial rolling reduction is about 50% to 80%, and the final rolling reduction is about 50% to 80%. The rate is about 50% to 85% and 0.15mm to 0.35mm
The final cold-rolled sheet thickness shall be . After the final cold rolling, the steel plate finished to the product thickness is surface degreased and then subjected to a decarburization primary recrystallization annealing treatment in wet hydrogen at 750°C to 850°C. After that, Al ₂ O ₃ , ZrO ₂ or TiO ₂ was applied to the surface of the steel plate.
Apply an annealing separator mainly composed of MgO, etc.
The present invention is applicable regardless of whether forsterite is formed or not. In order to prevent the formation of a forsterite film after final annealing, it is necessary to increase the content of an inert annealing separator such as Al ₂ O ₃ . After that, secondary recrystallization annealing is performed, but this step is carried out to sufficiently develop secondary recrystallized grains with {110}<001> orientation, and is usually box annealed to immediately raise the temperature to 1000℃ or higher. This is done by heating and holding at that temperature. In this case, in order to develop a highly uniform secondary recrystallized grain structure in the {110}<001> orientation, it is advantageous to perform retention annealing at a low temperature of 820°C to 900°C.
In addition, slow heat annealing at a heating rate of 0.5 to 15° C./h may also be used. The blunting annealing after the secondary recrystallization annealing is performed in dry hydrogen.
It is necessary to perform annealing at 1100°C or higher for 1 to 20 hours to achieve dulling of the steel plate. Next, in the present invention, after purification annealing, the oxide film on the surface of the steel sheet is removed using a strong acid such as sulfuric acid, nitric acid, or hydrofluoric acid. Further, this oxide removal may be performed by mechanical grinding. After this oxide removal treatment, the surface of the steel plate is finished to a mirror-like state, that is, to a center line average roughness of 0.4 μm or less, by a conventional method such as chemical polishing or electrolytic polishing. After that, the steel plate surface is heated with H ₂ and N ₂ and/or Ti compound gas such as TiCl ₂ , TiCl ₃ or TiCl ₄ .
By CVD treatment in a mixed gas with CH ₄ ,
After forming an ultra-thin tension coating of TiN, TiC or Ti(CN) on the plate surface, it is essential to annealing it in an H ₂ atmosphere at a temperature range of 600°C to 1000°C. If the annealing temperature in this H ₂ atmosphere is lower than 600℃, the reaction of TiCl ₄ etc. will be slow, and if it exceeds 1000℃, the steel plate will bend more and the magnetic properties will deteriorate. Must be in the 1000℃ range. Also, the annealing time in _H2 depends on the annealing temperature, but usually
Approximately 10 minutes to 50 hours is appropriate. The magnetic properties of the steel sheet treated as described above are further improved by applying an insulating coating containing phosphate and colloidal silica as the main components. The silicon steel plate treated as described above can be subjected to flattening heat treatment. (Example) Example 1 C: 0.043%, Si: 3.42%, Mn: 0.063%,
After homogenizing a hot rolled sheet containing Mo: 0.025%, Se: 0.022%, and Sb: 0.025% at 900°C for 3 minutes,
Cold rolling was performed twice with intermediate annealing at 950°C to obtain a final cold rolled sheet with a thickness of 0.23 mm. After decarburization annealing in wet hydrogen at 820°C, an annealing separator containing Al ₂ O ₃ (70%) and MgO (30%) as main components was applied to the surface of the steel sheet, followed by secondary re-treatment at 850°C for 50 hours. Crystal annealing was performed, followed by purification annealing in dry hydrogen at 120°C for 8 hours. After removing the oxide film by pickling, 3% HF
and chemical polishing in H ₂ O ₂ solution to give a mirror finish. After that, an ultra-thin tension film of TiN (0.65μm) was formed on the steel plate surface by a CVD reaction at 780℃ for 15 hours in a TiCl ₄ , H ₂ and N ₂ gas atmosphere using a CVD device, and then heated at 700℃. Hydrogen annealing was performed for 15 hours.
The magnetic properties of the product at that time were as follows. B ₁₀ : 1.92T, W _17/50 : 0.62W/Kg Example 2 C: 0.058%, Si: 3.36%, Mn: 0.080%, Al:
0.025%, S: 0.028%, N: 0.0068%, Cu: 0.1
%, Sn: 0.05% hot-rolled sheet at 1150℃
After uniform annealing for 30 minutes, rapid cooling treatment is performed, and then 300 minutes
The final cold-rolled sheet with a thickness of 0.20 mm was obtained by rolling at a temperature of ℃. After decarburization annealing in wet hydrogen at 850℃, the surface
After applying an annealing separator mainly composed of Al ₂ O ₃ (80%) and MgO (20%), the temperature was increased from 850℃ to 1150℃ at 8℃/
After secondary recrystallization by raising the temperature to hr, purification annealing was performed in dry hydrogen at 1200°C for 8 hours. Thereafter, the oxide film was removed by pickling, and then chemical polishing was performed in a 3% HF and H _{2 O} solution to give a mirror finish. Then use CVD equipment to combine TiCl ₄ , H ₂ and N _2.
After forming an ultra-thin tension film of Ti (C, N) on the surface of the steel sheet by CVD reaction at 800°C for 17 hours in a CH ₄ mixed gas, annealing was performed in H ₂ at 800°C for 10 hours. Thereafter, this surface was further treated with an insulating coating mainly composed of phosphate and colloidal silica. The magnetic properties of the product at that time were as follows. B ₁₀ : 1.92T, W _17/50 : 0.59W/Kg (Effect of the invention) Each of the above inventions uses TiC by applying the CVD method,
In addition to maximizing the properties of the ultra-thin tensile coating made of TiN or Ti (C, N), it also contributes to the purification of steel sheets, and is useful for ultra-low core loss of unidirectional silicon steel sheets. be.

Claims (1)

[Claims] 1. After removing oxides on the surface of a finish-annealed unidirectional silicon steel sheet and finishing it to a mirror-like state with an average central roughness of 0.4 μm or less, CVD treatment is applied to the surface of the steel sheet. An ultra-low iron loss unidirectional silicon steel sheet is produced by forming an ultra-thin tensile film of TiN, TiC or Ti(CN), and then annealing it in an _H2 atmosphere at a temperature range of 600 to 1000℃. Production method. 2 After removing the oxides on the surface of the finish-annealed unidirectional silicon steel sheet and finishing it to a mirror-like state with an average central roughness of 0.4 μm or less, TiN, TiC or Ti(CN) is applied to the surface of the steel sheet by CVD treatment. ) is formed, and then annealed in a H ₂ atmosphere at a temperature range of 600 to 1000°C, and an insulating film containing phosphate and colloidal silica as main components is further coated on the tension film. A method for producing an ultra-low core loss unidirectional silicon steel sheet.